The TONICELLIDAE were part of the ISCHNOCHITONIDAE before. The genus Tonicella proper is arctic, and best known from the Tonicella marmorea, which is a splendid beautiful Chiton, common for example when diving in the Lofoten Islands.The TONICELLIDAE has 5 different genera today.
For a list of genera and species:
http://www.marinespecies.org/aphia.php?p=taxdetails&id=385500